1. Field of the Invention
The present invention relates generally to lithographic methods employed for fabricating microelectronic fabrications. More particularly, the present invention relates to electron beam dosage compensation lithographic methods employed for fabricating microelectronic fabrications.
2. Description of the Related Art
Microelectronic fabrications are formed from microelectronic substrates over which are formed patterned microelectronic conductor layers which are separated by microelectronic dielectric layers. In the process of forming patterned microelectronic conductor layers within microelectronic fabrications, as well as in the process of forming other types of patterned microelectronic layers within microelectronic fabrications, further as well as in the process of forming patterned masking layers within photomasks which may be employed for forming patterned microelectronic layers of various varieties within microelectronic fabrications, there may be employed direct lithographic writing methods, such as but not limited to direct electron beam lithographic writing methods, to form within a blanket photoresist layer a latent electron beam exposed pattern which upon subsequent development provides a patterned photoresist mask for: (1) etching within a microelectronic fabrication a blanket microelectronic layer formed beneath the patterned photoresist mask to form a patterned microelectronic layer formed beneath the patterned photoresist mask; or in the alternative (2) etching within a photomask a blanket masking layer formed beneath the patterned photoresist mask to form a patterned masking layer formed beneath the patterned photoresist mask.
While direct electron beam lithographic methods are thus desirable within the art of microelectronic fabrication for forming electron beam exposed and subsequently patterned photoresist layers which are employed either directly or indirectly for forming patterned microelectronic layers within microelectronic fabrications, direct electron beam lithographic methods are nonetheless not entirely without problems in the art of microelectronic fabrication for forming electron beam exposed and subsequently patterned photoresist layers which are employed either directly or indirectly for forming patterned microelectronic layers within microelectronic fabrications.
In that regard, it is known in the art of microelectronic fabrication that electron beam exposed (directly written) and subsequently developed patterned photoresist layers are often difficult to form with uniform and anticipated linewidth resolution and fidelity encompassing various areal densities of patterned photoresist layers within microelectronic fabrications insofar as electron beam radiation when employed for directly forming patterned photoresist layers within microelectronic fabrications scatters from either within a blanket photoresist layer which is directly exposed while employing electron beam radiation (i.e., forward scattering), or in the alternative electron beam radiation also scatters from a substrate over which is formed a blanket photoresist layer which is directly exposed employing electron beam radiation (i.e., back scattering). Such forward scattering or back scattering leads to pattern density related inhomogeneity effects, such as pattern resolution inhomogeneity effects and patterned fidelity inhomogeneity effects, such inhomogeneity effects generally known in the art of microelectronic fabrication as proximity effects.
It is thus towards the goal of providing within the art of microelectronic fabrication methods and materials through which there may be attenuated proximity effects when exposing a blanket photoresist layer while employing an electron beam method in the process of forming from the blanket photoresist layer a patterned photoresist layer, such that a patterned microelectronic layer formed while employing the patterned photoresist layer as an etch mask may similarly also be formed with uniform and anticipated linewidth resolution and fidelity.
It is towards the foregoing objects that the present invention is directed.
Various methods have been disclosed in the art of microelectronic fabrication for forming with enhanced linewidth resolution within microelectronic fabrications or enhanced linewidth fidelity within microelectronic fabrications patterned microelectronic layers within microelectronic fabrications.
For example, Abate et al., in U.S. Pat. No. 5,656,399, discloses a method for fabricating an x-ray photomask wherein there is compensated for non-collimated x-ray beam exposure effects such as global divergence, local divergence and dose non-uniformity within a patterned photoresist layer which is formed from a blanket photoresist layer formed over a microelectronic substrate while employing the x-ray photomask. To realize the foregoing object, the method provides for an adjustment within the x-ray photomask of the locations of patterned features within the x-ray photomask such as to compensate for the non-collimated x-ray beam exposure effects.
In addition, Kim, in U.S. Pat. No. 5,804,339, discloses an electron beam exposure method for forming for use when fabricating a microelectronic fabrication a photomask with an enhanced fidelity ratio of a series of patterned features within the photomask. To realize the foregoing object, the electron beam exposure method employs when fabricating the photomask, and in addition to a primary electron beam exposure of a blanket photoresist layer employed for forming the photomask, a secondary electron beam correction exposure of the blanket photoresist layer, where the secondary electron beam correction exposure is in a range of from about 0.75 to about 2.25 percent of the primary electron beam exposure.
Further, Tzu et al., in U.S. Pat. No. 5,994,009, discloses an electron beam exposure method for forming within a microelectronic fabrication a patterned microelectronic layer within attenuated proximity effect, in particular under circumstances where the patterned microelectronic layer is formed over a topographically varied substrate layer. To realize the foregoing object, the method employs when forming a photomask employed for forming the patterned microelectronic layer: (1) a first proximity effect correction which is directed towards an optical (i.e., electron beam exposure) proximity effect within the photomask; and (2) a second proximity effect correction which is directed towards a process related (i.e., topographic substrate) proximity effect within the photomask.
Finally, Gerber et al., in U.S. Pat. No. 6,035,113, discloses a method for efficiently compensating for a proximity effect when fabricating while employing an electron beam lithographic method a photomask, even under circumstances where there is employed when fabricating the photomask a complex hierarchal design data set. To realize the foregoing object, the method employs a multiple gaussian approximation, where short term gaussian terms are treated as forward scatter terms and long term gaussian terms are treated as back scatter terms.
Desirable in the art of microelectronic fabrication are additional methods and materials which may be employed for attenuating when exposing a blanket photoresist layer while employing an electron beam method proximity effects.
It is towards the foregoing object that the present invention is directed.
A first object of the present invention is to provide an electron beam method for exposing a blanket photoresist layer.
A second object of the present invention is to provide an electron beam method in accord with the first object of the present invention wherein there is attenuated a proximity effect when exposing the blanket photoresist layer while employing the electron beam method.
A third object of the present invention is to provide a method in accord with the first object of the invention and the second object of the invention, wherein the method is readily commercially implemented.
In accord with the objects of the present invention, there is provided by the present invention a method for forming a patterned layer within a microelectronic fabrication. To practice the method of the present invention, there is first provided a substrate. There is then formed over the substrate a blanket target layer. There is then formed over the blanket target layer a blanket photoresist layer. There is then exposed, while employing a radiation beam method susceptible to a proximity effect, the blanket photoresist layer to form an exposed blanket photoresist layer which comprises: (1) a main latent pattern comprising a first series of latent patterns; and (2) a second latent pattern comprising a second series of latent patterns adjacent the first series of latent patterns. There is then developed the exposed blanket photoresist layer to form a corresponding patterned photoresist layer comprising: (1) a corresponding main photoresist pattern comprising a first series of patterned photoresist layers; and (2) a corresponding second photoresist pattern comprising a second series of patterned photoresist layers adjacent the first series of patterned photoresist layers. There is then etched, while employing an etchant, and while employing the patterned photoresist layer as an etch mask layer, the blanket target layer to form a patterned target layer, wherein: (1) each patterned photoresist layer within the first series of patterned photoresist layers has a first linewidth such that not all of a first portion of the blanket target layer beneath the main photoresist pattern is completely etched within the etchant; and (2) each patterned photoresist layer within the second series of patterned photoresist layers has a second linewidth such that all of a second portion of the blanket target layer beneath the second photoresist pattern is completely etched within the etchant.
The present invention is particularly useful when fabricating a photomask while employing the method of the present invention.
The present invention provides an electron beam method for exposing a blanket photoresist layer, where there is attenuated a proximity effect when exposing the blanket photoresist layer while employing the electron beam method. The present invention realizes the foregoing object in part by employing when exposing a blanket photoresist layer while employing an electron beam method: (1) a main latent pattern comprising a first series of latent patterns; and (2) a second (dummy) latent pattern comprising a second series of latent patterns adjacent the first series of latent patterns, wherein upon developing the main latent pattern to form a main photoresist pattern comprising a first series of patterned photoresist layers and developing the second latent pattern to form a second photoresist pattern comprising a second series of patterned photoresist layers: (1) each patterned photoresist layer within the first series of patterned photoresist layers has a first linewidth such that not all of a first portion of a blanket target layer formed beneath the main photoresist pattern is completely etched within an etchant; and (2) each patterned photoresist layer within the second series of patterned photoresist layers has a second linewidth such that all of a second portion of the blanket target layer formed beneath the second photoresist pattern is completely etched within the etchant.
The present invention is readily commercially implemented. The present invention employs methods and materials as are generally known in the art of microelectronic fabrication, but employed within the context of particular design limitations which provide at least in part the present invention. Since it is at least in part a design limitation which provides the present invention, rather than the existence of methods and materials which provides the present invention, the method of the present invention is readily commercially implemented.